FILE- In this March 7, 2017, file photo, then-Deputy Attorney General-designate Rod Rosenstein, listens on Capitol Hill in Washington, during his confirmation hearing before the Senate Judiciary Committee. The author of a scathing memo that the White House used to help justify the firing of FBI Director James Comey is also overseeing a Justice Department investigation into Russian interference in the 2016 election. In a three-page rebuke of Comey's conduct, Rosenstein said the FBI director had usurped the attorney general's authority last year when he announced that the FBI was closing its investigation of Hillary Clinton's use of a private email as secretary of state. (AP Photo/J. Scott Applewhite, File)
(J. Scott Applewhite)

Deputy Attorney General Rod Rosenstein reportedly threatened to resign from his position after the White House cast him as the prime person behind the decision to fire FBI Director James Comey.

Sources close to the White House reported that President Donald Trump had made up his mind to dismiss the FBI director by last weekend following Comey's latest congressional testimony, according to the Washington Post.

Trump told Vice President Mike Pence and senior aides on Monday that he was ready to fire Comey, but first wanted to talk with Attorney General Jeff Sessions and Rosenstein and summoned them to the White House for a meeting, the newspaper reported.

Although Trump had already decided to fire Comey, sources told the Post that the president directed Sessions and Rosenstein to explain the case against the FBI director in writing, which they in turn did, according to reports.

The president fired Comey the next day, a move White House Press Secretary Sean Spicer said occurred "based on the clear recommendations of both Deputy Attorney General Rod Rosenstein and Attorney General Jeff Sessions."

Deputy Press Secretary Sarah Huckabee Sanders also disputed reports that Trump pushed for the firing, saying that Rosenstein and Sessions came to him about Comey.

"He'd been considering letting Director Comey go since the day he was elected," she told reporters. "But he did have a conversation with the Deputy Attorney General on Monday, where they had come to him to express their concerns. The president asked they put those concerns and their recommendation in writing."

Sanders added that it was "absolutely" the White House's assertion that Rosenstein had decided on his own to review the FBI director's performance.

White House officials announced Tuesday evening that Trump had fired Comey, who had been appointed to 10-year term with the FBI in 2013.

The president, in a letter to the FBI director, said the dismissal was needed to restore "public trust and confidence" in the agency. Comey had come under fire following his investigation into 2016 Democratic presidential nominee Hillary Clinton's email practices -- particularly in the final days before voters were set to hit the polls.